1. Field of the Invention
The invention relates to fluid flow control valves and, more particularly, to a fluid flow control valve having an orifice that defines a seat. An elastomeric diaphragm is urged against the seat by a pressure differential occurring across the diaphragm so that fluid flows through flow control passages defined between the diaphragm and the seat. Increasing pressure differential across the diaphragm causes the diaphragm to constrict the flow control passages through deflection of the diaphragm.
2. Description of Related Art
Fluid flow control valves are used for regulating fluid flow to a substantially constant flow rate over a range of pressure differentials, such as about 0.1 bar to 10 bars. In such valves, the diaphragm typically comprises a solid body of elastomeric material. When urged against a seat of an orifice, the diaphragm deforms, the degree of deformation increasing with increasing pressure differential across the diaphragm. As the deformation of the diaphragm increases, the flow control passages between the diaphragm and the seat become smaller. The valve is designed such that over the range of pressure differentials of interest, the changing flow area of the flow control passages offsets the changing pressure differential so as to maintain the flow rate substantially constant.
U.S. Pat. No. 6,390,122 to Zhang, et al. and assigned to the assignee of the present invention describes a fluid flow control valve that has a housing with a fluid flow passage that extends therethrough between openings for flow into and out of the fluid flow passage. An orifice with a seat at one end is disposed in the passage, and a diaphragm is disposed in the passage so that an end face of the diaphragm opposes the seat of the orifice. The seat is configured so that one or more flow control passages are defined between the seat and the end face of the diaphragm. In normal forward flow through the valve, fluid flows between the outer peripheral surface of the diaphragm and the inner surface of the housing and then is turned radially inwardly by the orifice and flows through the flow control passages between the end face of the diaphragm and the orifice seat. The seat can be contoured to include at least two different shapes of channels, each promoting localized bending of the diaphragm at a different pressure differential and thereby permitting an expansion of the working pressure range to very low pressure differentials.
The valve described above is designed to control the flow of fluids over a particular range of pressure differentials and to achieve a particular desired flow rate. Therefore, different valves formed of different components are typically manufactured for achieving different desired flow rates. This increases the cost and complexity of the manufacturing process. Thus, there exists a need for an improved device that can control the flow of fluids over a range of pressure differentials. The device should be cost efficient to manufacture, and preferably should provide a long service life.
The present invention provides a fluid flow control valve and an orifice for such a valve. The orifice defines two seats against which a diaphragm of the valve can be urged. Each seat defines a particular contour, including one or more channels, slots, and or protrusions that form flow control passages through which fluid flows between the diaphragm and the orifice. The orifice can be placed in either of two orientations so that either seat can be disposed toward the diaphragm. As the pressure differential across the valve increases, the diaphragm is urged more firmly against the seat facing the diaphragm and the diaphragm partially closes the flow control passages, thereby regulating the flow to a substantially uniform volumetric rate. The contours of the two seats can be the same, or each seat can be different to provide a unique controlled flow rate. Thus, the orifice and the valve of the present invention can be used to control a flow of fluid to multiple desired flow rates over a range of pressure differentials, thereby reducing the cost and complexity of the manufacturing process.
According to one embodiment of the present invention, the valve includes a housing that defines a fluid flow passage and an orifice disposed in the fluid flow passage. Each of the first and second seats of the orifice has a main support surface that defines at least one channel, slots, and/or protrusions. A deformable and bendable elastomeric diaphragm is disposed in the fluid flow passage with an end face disposed toward one of the seats of the orifice and urged thereagainst by the flow of fluid through the valve. The orifice can be reversed in the housing so that the diaphragm is disposed against the opposite one of the seats. The diaphragm can also be reversible and can define identical contours on either side. A retainer with a plurality of legs can be provided for engaging the housing and retaining the diaphragm in a coaxially aligned configuration with the orifice. According to one aspect of the invention, an outer surface of the orifice defines frustoconical portions for engaging an inner mating portion of the housing. According to another aspect, the orifice can define a groove on its outer surface for receiving a sealing ring that engages the mating portion of the housing.